Multi-lamp arrangement for optical systems

ABSTRACT

A multi-lamp arrangement for optical systems includes plural lamps and a collective light guide, where each lamp is positioned such as to transmit light into respective light guides that are both optically connected to the collective light guide. In one embodiment, one of the lamps is optically connected to the collective light guide by a mirror and-prism arrangement and an intermediate light guide and an intermediate mirror-and-prism arrangement. An augmented color modulator may be provided with a number of color fields, where the number of identical color fields is equal to the number of lamps.

CROSS RERERENCE TO RELATED APPLICATIONS

This application is a division of co-pending application Ser. No. 10/427,946, filed on May 2, 2003, which claimed benefit of provisional application No. 60/377,250, filed on May 3, 2002, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to field of optical systems, and more specifically to a multi-lamp arrangement for optical systems comprising two lamps or more and a collective light guide.

BACKGROUND ART

Modem optical systems, such as state of the art image projectors which are quite compact, rely on light sources with high light intensity. Image projectors are also increasingly being used in e.g. simulation systems, which require very sharp and bright images. With the known lamp technology, it very difficult to produce high brightness images from projectors, without having to use high power light sources. Today, similar brighness levels in projectors are obtained by high power Xenon lamps.

Most image projectors use ultra-high-pressure (UHP) lamps with a short arc gap. Lamps termed “short arc gap” typically have an arc gap in the range between 1.0 mm and 1.5 mm. The light emitted by short arc gap lamps has a much better light collection than light emitted by lamps with larger arc gaps, and thus a very good visible light efficiency. It is thus desirable to use lamps with an arc gap as short as possible in modern image projectors, in order to produce the brightest possible image.

Short arc gap lamps are, however, only available at comparatively lower power outputs (e.g. 1.0 mm at 150 W and 1.4 mm at 300 W). In order to produce high quality images by projectors, it is therefore known to arrange two or more short arc lamps in a system.

One such multi-lamp system utilizes an assembly of 4 short arc gap lamps, in a quadratic configuration, each lamp having a parabolic reflector with a condenser lens that focuses the light into a common light guide. This assemly is able to gain 1.5 times the flux of a single lamp system. Typical lamp arc gap for such system is 1.0 mm to 1.3 mm.

It is therefore a need for a multi-lamp system that produces a flux level that is equal to or better than known systems, but with fewer lamps, thus yielding reduced material cost, manufaturing cost and operating costs, reduced power consumption and reduced product temeperature, compared to known systems.

The invented system may utilize shorter arc gap lamps than the presently known technology, thus producing a better image performance.

DISCLOSURE AND SUMMARY OF THE INVENTION

The present invention meets the above mentioned need, in that it provides a multi-lamp arrangement for optical systems comprising two lamps or more and a collective light guide, characterized in that each lamp is positioned such as to transmit light into respective light guides that are both optically connected to the collective light guide.

The invention also provides an augmented color modulator with a number of color fields, for use in an image projector comprising two lamps or more, characterized by the number of identical color fields being equal to the number of lamps.

Preferred embodiments of the invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an embodiment of the invention

FIG. 2 a is a schematic plan view of another embodiment of the invention, including also individual color modulators.

FIG. 2 b is a schematic view of a color modulator.

FIG. 3 is a schematic plan view of the embodiment depiced in FIG. 1, but also showing a common, augmented color modulator.

FIG. 4 is a schematic view of the augmented color modulator.

FIG. 5 is a schematic plan view of the embodiment shown in FIG. 1, but with a color modulator positioned on the exit side of the collective light guide.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

FIG. 1 is a schematic plan view of an embodiment of the invention, and shows an arrangemnent comprising two lamps 10, 15, each emitting light schematically illustrated by exemplary light beams 20. The person skilled in the art will understand that the system according to the invention may comprise more lamps than two and be arranged in any configuration.

In general, the multi-lamp arrangement for optical systems according to the invention comprises two or more lamps 10, 15, each lamp positioned such as to transmit light 20 into respective light guides 36, 46 that are both optically connected to a collective light guide 58, out of which the light may be transmitted in any optical system (not shown).

In one configuration (cf. FIG. 2A), one light guide 36 is optically connected to the collective light guide 58 by means of a mirror 38 and a prism 40. FIG. 2A shows the lamps having individual color modulators 14, 18 positioned between each lamp and their respective light guides, but this is merely to illustrate one application of the multi-lamp arrangement. The color modulator may be any type of sequential color filter system, such as color wheel, color switch, etc., without departing from the the scope of the invention. The invention is not restricted to use with a color modulator, but works equally well with a 3-chip system with color separation (e.g. Philips Prism). The color modulator may also be positioned on the exit side (cf. FIG. 5) or entrance side (not shown) of the collective light guide 58.

The color modulator may be a conventional color wheel, of which one example is shown in FIG. 2B as having blue (B), white (W), green (G) and red (R) color fields. FIG. 1 shows a second embodiment, where the lamps are arranged such that a lamp 10 is optically connected to the second light guide 36 by means of an intermediate light guide 30 and an intermediate mirror 32 and prism 34. Here, the lamps are arranged in a side-by-side relationhip, projecting its respective light beams in the same general direction.

In the embodiment shown in FIG. 2A, the first lamp 15 is arranged to project its respective light beams in a direction that is generally perpendicular to the direction of the light emitted from the second lamp. Any lamp orientation is, however, conceivable for a person skilled in the art.

The embodiment of FIG. 1 is shown in FIG. 3, but with an augmented color modulator 62 positioned between each lamp and the intermediate light guide 30 and the first light guide 46, respectively.

This augmented color modulator 62 comprises a number of color fields (R, B, W, G), but arranged such that the number of identical color fields are equal to the number of lamps. FIG. 4 shows an example of such augmented color modulator, and the fact that the color fields are arranged sequentially: R-B-W-G, R-B-W-G. In the case of a two-lamp system, each color field is arranged diagonally of its respective identical color field. The color modulator is synchronized such that similar respective color fields will be collected into the respective light guides simultaneously.

As shown in FIGS. 2A and 3, the color modulator (14, 18; 62) may generally be positioned in or near the respective lamps' second focal point.

Although it is common to use UHP type lamps, the invention is directed to any type of lamp, including but not limited to metal halide type lamps, or xenon lamps.

Using a two-lamp system, the light guides' entrance aperture will be approximately half the size than for a single lamp system. Thus, in general, the entrance aperture dimensions of each the first 46, second 36 and intermediate 30 light guide each are in the order of one half the entrance aperture dimension of the collective light guide 58. Even more general, for a multi-lamp arrangement, each of the light guide entrance apertures have individual aperture dimensions approximately or exactly equal to the collective light guide 58 aperture dimension divided by the number of lamps.

The light guide may be any appropriate light guide, for example a rod comprising either a solid translucent body or a number of mirrors glued together, forming a tunnel.

LIST OF COMPONENTS SHOWN IN THE FIGURES

-   10 second lamp -   11 second reflector -   12 second burner -   14 second color modulator -   15 first lamp -   17 first reflector -   19 first burner -   18 first color modulator -   20 light beam -   30 intermediate light guide -   32 intermediate mirror -   34 intermediate prism -   36 second light guide -   38 second mirror -   40 second prism -   46 first rod -   58 collective light guide -   62 augmented color modulator 

1. A multi-lamp arrangement for optical systems, comprising: first and second lamps (15, 10) arranged side by side; first and second light guides (46, 36) connected respectively to the first and second lamps, the first light guide being generally perpendicular to the second light guide; and a collective light guide (58) connected to the first and second light guides, wherein, each lamp is positioned to transmit light into the collective light guide via the respective first and second light guides, and light from the first lamp travels in the first light guide in a generally perpendicular direction to light from the second lamp travelling in the second light guide.
 2. The multi-lamp arrangement of claim 1, further comprising a first mirror (39) located intermediate the collective light guide (58) and the second light guide (36), the first mirror optically connecting the second light guide to the collective light guide.
 3. The multi-lamp arrangement of claim 2, wherein the first mirror is a first mirror and prism arrangement.
 4. The multi-lamp arrangement of claim 2, further comprising a second mirror (32) located intermediate the second lamp (10) and the second light guide (36), the second mirror optically connecting the second lamp to the second light guide and changing a direction of travel of the light from the second lamp.
 5. The multi-lamp arrangement of claim 4, further comprising an intermediate light guide (30) located intermediate the second mirror (32) and the second lamp (10), the intermediate light guide optically connecting the light from the second lamp to the second mirror.
 6. The multi-lamp arrangement of claim 5, wherein, light from the first lamp travels in the first light guide in a generally parallel direction to light from the second lamp travelling in the intermediate light guide.
 7. The multi-lamp arrangement of claim 1, further comprising color modulators (14, 18) positioned to modulate the light from the first and second lamps.
 8. The multi-lamp arrangement of claim 7, wherein the color modulators (14, 18) are positioned between the first and second lamps and the first and second light guides.
 9. The multi-lamp arrangement of claim 7, wherein the color modulators (14, 18) are positioned at an exit side of the collective light guide.
 10. The multi-lamp arrangement of claim 7, wherein one of the color modulators is positioned between the first lamp and the first light guide and another of the color modulators is positioned between the second lamp and the intermediate light guide.
 11. The multi-lamp arrangement of claim 7, wherein the color modulators are positioned in or near the respective lamps' second focal point.
 12. The multi-lamp arrangement of claim 1, wherein the lamps are UHIP lamps.
 13. The multi-lamp arrangement of claim 1, wherein the lamps are metal halide lamps.
 14. The multi-lamp arrangement of claim 1, wherein the lamps are any light source.
 15. The multi-lamp arrangement of claim 1, wherein entrance apertures dimensions of each the first and second light guides each are in the order of one half an entrance aperture dimension of the collective light guide.
 16. The multi-lamp arrangement of claim 1, wherein each of the first and second light guide entrance apertures have individual aperture dimensions approximately or exactly equal to the collective light guide aperture dimension divided by the number of lamps.
 17. The multi-lamp arrangement of claim 1, wherein at least one of the first and second light guides is optically connected to the collective light guide by a mirror-and-prism arrangement.
 18. The multi-lamp arrangement of claim 1, wherein the first and second light guides are oriented in a generally perpendicular relationship.
 19. A multi-lamp arrangement, comprising: two lamps, each lamp emitting a light beam; a light guide connected to each of the lamps to receive and transmit the light beam of each light; and a collective light guide connected at an exit of each of the light guides to receive the light beam exiting each light guide, wherein, the light transmitted in one of the light guides travels in a generally perpendicular direction to the light transmitted in another of the light guides. 